The present invention is related generally to lobe-type pumps and more specifically to timed element, dual shaft lobe pumps for use in high pressure and industrial applications.
Lobe-type pumps are known in the art and traditionally have utility in sanitary applications including food products. The rotation of the lobes or impellers is timed so that the lobes do not come into contact with one another.
Many lobe pumps have been limited to low pressure applications, or pressures of less than 200 psi because each shaft is supported on one side of the lobe only. Specifically, because the pumping chamber is sealed for sanitary reasons, the shafts are supported with bearings disposed outside of the sealed pump chamber. The distal ends of the shafts are therefore not supported and because of the seals disposed between the bearings and the lobes, there is a substantial distance between the supporting bushings and the lobes. As a result, operation of the pumps are limited to pressures of less than 200 psi. Otherwise, the strain on the shafts can result in engagement between the lobes or between the lobes and the casing or head plate. Thus, the distance between the bearings and the lobes unduly limits the pressures at which these pumps can operate.
Accordingly, there is a need for an improved lobe pump design with an improved bearing placement which will enable lobe pumps to operate under high pressure conditions and which will expand the applicability of lobe pumps to different industrial applications.
A second problem associated with currently available lobe pumps is the positioning of the pumping elements or lobes during assembly of the pumps. Specifically, current designs require the employment of several shims which are typically 0.005" to 0.010" thick in order to accurately place the lobes in the desired position in the pumping chamber. The plastic shims are not very durable and, in the event the shims need to be replaced, the pump often needs to be sent back to the factory for service. Thus, not only is the assembly of lobe pumps more costly due to the employment of shims, the operation and use of lobe pumps is more expensive because the shims can be easily damaged or lost during routine servicing of the lobe pump. Accordingly, it would be beneficial to provide an improved lobe pump whereby the lobes or pumping elements can be accurately positioned within the casing or pumping chamber without the employment of shims.
Another disadvantage of currently available lobe pumps is the relatively low speed in which these pumps can be operated. The lower speeds are required due to the design of the pump casing or pump chamber which traditionally is required to be sanitary due to the use of lobe pumps in the food industry. Thus, it would be beneficial to provide an improved lobe pump casing and head plate design which would enable a lobe pump to be operated at higher speeds than conventional lobe pumps.
Still another problem associated with the employment of currently available lobe pumps is the use of customized seals in these pumps to isolate the pumping chamber from the timing gears and thrust bearings. The seals are often custom made and not readily available. Further, in addition to employing more expensive seals, it is difficult to replace seals in a lobe pump because the wet end of the pump must be disassembled in order to replace the seals. Accordingly, it would be desirable to provide a new lobe pump design which would provide fast and easy access to the seal for easy replacement thereof. Further, it would be desirable to provide a new lobe pump design which would utilize standard, "off-the-shelf" seals as opposed to custom made seals. Such a pump would be cheaper to manufacture and to maintain.
As a result of the above deficiencies, lobe pumps are relatively limited in their use. An improved lobe pump design would expand the applicability of lobe pumps beyond the food, beverage and dairy industries and beyond other low pressure applications.